package com.zmd.common_class_libraries;

import java.util.Map;

/**
 * @ClassName SystemExample
 * @projectName: object1
 * @author: Zhangmingda
 * @description： XXX
 * date: 2021/4/6.
 */
public class SystemExample {
    public static void main(String[] args) {
        Map<String, String> envMap = System.getenv();
        for (String key : envMap.keySet()) {
            String value = envMap.get(key);
            System.out.println(key  + "=" + value);
        }
        System.out.println("-------------------------");
        System.out.println(System.getenv("JAVA_HOME"));
    }
}

package com.zmd.common_class_libraries;

import java.io.IOException;

/**
 * @ClassName RuntimeExample
 * @projectName: object1
 * @author: Zhangmingda
 * @description： XXX
 * date: 2021/4/6.
 */
public class RuntimeExample {
    public static void main(String[] args) throws IOException {
        //不用new关键字，直接用类的静态方法，获取当前运行时环境
        Runtime runtime = Runtime.getRuntime();
        //获取CPU核心数
        System.out.println("处理器数量：" + runtime.availableProcessors());
        //获取可用最大内存
        System.out.println("最大可用内存：" + runtime.maxMemory());
        //获取java虚拟机的总内存大小
        System.out.println("JAVA虚拟机总内存totalMemeory:" + runtime.totalMemory());
        //空闲内存
        System.out.println("空闲内存：" + runtime.freeMemory());

        //通过java启动系统exe文件例如QQ音乐
        runtime.exec("\"C:\\Program Files (x86)\\Tencent\\QQMusic\\QQMusic.exe\"");

    }
}